Tracing of particulate organic C sources across the terrestrial-aquatic continuum, a case study at the catchment scale (Carminowe Creek, southwest England)

M Glendell; R Jones; J A J Dungait; K Meusburger; A C Schwendel; R Barclay; S Barker; S Haley; T A Quine; J Meersmans

doi:10.1016/j.scitotenv.2017.10.211

Tracing of particulate organic C sources across the terrestrial-aquatic continuum, a case study at the catchment scale (Carminowe Creek, southwest England)

Sci Total Environ. 2018 Mar:616-617:1077-1088. doi: 10.1016/j.scitotenv.2017.10.211. Epub 2017 Nov 6.

Authors

M Glendell¹, R Jones², J A J Dungait³, K Meusburger⁴, A C Schwendel⁵, R Barclay², S Barker⁶, S Haley², T A Quine², J Meersmans⁷

Affiliations

¹ The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, UK. Electronic address: Miriam.Glendell@hutton.ac.uk.
² University of Exeter, Geography-College of Life and Environmental Sciences, Exeter EX4 4RJ, UK.
³ Sustainable Agriculture Science, Rothamsted Research, North Wyke, Okehampton, Devon, EX20 2SB, UK.
⁴ Environmental Geosciences, University of Basel, Bernoullistrasse 30, 4056 Basel, Switzerland.
⁵ School of Humanities, Religion & Philosophy, York St John University, Lord Mayor's Walk, York YO31 7EX, UK.
⁶ Environment and Sustainability Institute, University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE, UK.
⁷ School of Water, Energy and Environment, Cranfield University, Bedford MK43 0AL, UK.

PMID: 29107375
DOI: 10.1016/j.scitotenv.2017.10.211

Abstract

Soils deliver crucial ecosystem services, such as climate regulation through carbon (C) storage and food security, both of which are threatened by climate and land use change. While soils are important stores of terrestrial C, anthropogenic impact on the lateral fluxes of C from land to water remains poorly quantified and not well represented in Earth system models. In this study, we tested a novel framework for tracing and quantifying lateral C fluxes from the terrestrial to the aquatic environment at a catchment scale. The combined use of conservative plant-derived geochemical biomarkers n-alkanes and bulk stable δ¹³C and δ¹⁵N isotopes of soils and sediments allowed us to distinguish between particulate organic C sources from different land uses (i.e. arable and temporary grassland vs. permanent grassland vs. riparian woodland vs. river bed sediments) (p<0.001), showing an enhanced ability to distinguish between land use sources as compared to using just n-alkanes alone. The terrestrial-aquatic proxy (TAR) ratio derived from n-alkane signatures indicated an increased input of terrestrial-derived organic matter (OM) to lake sediments over the past 60years, with an increasing contribution of woody vegetation shown by the C₂₇/C₃₁ ratio. This may be related to agricultural intensification, leading to enhanced soil erosion, but also an increase in riparian woodland that may disconnect OM inputs from arable land uses in the upper parts of the study catchment. Spatial variability of geochemical proxies showed a close coupling between OM provenance and riparian land use, supporting the new conceptualization of river corridors (active river channel and riparian zone) as critical zones linking the terrestrial and aquatic C fluxes. Further testing of this novel tracing technique shows promise in terms of quantification of lateral C fluxes as well as targeting of effective land management measures to reduce soil erosion and promote OM conservation in river catchments.

Keywords: Biomarkers; Bulk stable (13)C and (15)N isotopes; Lateral carbon fluxes; Sediment fingerprinting; n-Alkanes.